Effects of Bed Roughness on Turbulent Characteristics of a Three-Dimensional Wall Jets

In this paper the experimental study of the flow pattern around a round wall jet has been carried out to investigate the effect of the bed roughness on the turbulence characteristics، including Reynolds stress and turbulence intensities. Measurements were conducted using the three-dimensional velocimeter، ADV and time series of the velocity components are used to investigate the variation of the turbulent flow parameters along the measuring domain. The results showed that by increasing the bed roughness، the streamwise and vertical turbulence intensities increase by downstream distance and for a specific bed roughness the streamwise turbulence intensity is higher than the vertical one. Furthermore، by going downstream from the jet entrance the bed shear stress reduces and by increasing the bed roughness، the bed shear stress has an increasing trend along the jet centerline. Location of the maximum bed shear stress does not change by changing the bed roughness.